1. Technical Field
The present invention relates to a fire alarm system having a fire receiver, terminal devices such as transmitters and fire detectors connected to the fire receiver, and devices to be controlled such as fire doors and local alarm sounding devices, and more particularly to the transmission of a fire signal, a control signal and the like between the terminal devices and between the fire receiver and the terminal devices.
2. Background Art
Recently, a polling-type fire alarm system has been employed in a building having a relatively large size. In a fire alarm system of the foregoing type, fire information (whether or not a fire signal is present and a physical quantity signal of a fire phenomenon) and control information (an operating command and a restoring command to the device to be controlled, and state signal of the device) are transmitted and received between a fire receiver and terminal devices disposed at various portions in the building, namely, supervisory terminals such as fire detectors and gas leakage detectors, transmitters to which devices to be controlled such as fire doors, smoke dampers and smoke barrier are connected, and analog fire detectors and the like. The fire receiver has an internal ROM (Read Only Memory) which previously stores the addresses of the terminal devices, contents to be displayed at the time of a fire, and linkage information about the devices to be controlled and the like. In accordance with the stored information, the transmitters and the analog fire detectors and the like are polled to collect fire information and information about the devices to be controlled. If information indicating the occurrence of fire has been determined from the fire information, the discriminated contents are displayed and the relative devices to be controlled are linkage-controlled.
Since the conventional polling-type fire alarm system has been constituted while using the fire receiver as the main device as described above, information cannot directly mutually be transmitted and received between the terminal devices such as the transmitters and the analog fire detectors. If information is transmitted and received between two transmitters for example, the fire receiver must be interposed. The reason for this is that the timing for the terminal device to transmit the signal is determined by the fire receiver without exception.
Therefore, the load for the fire receiver to bear is too heavy, and accordingly, a problem arises in that a failure of the fire receiver deteriorates the overall function of the system.
Further, in the conventional polling-type fire alarm system, the signal transmission between the fire receiver and the terminal devices has been performed while employing a predetermined signal length, that is, a fixed length. If a signal having a length except for the predetermined length is received, a discrimination is made that a transmission error has occurred. The reason for this is that the signal transmission rate between the fire receiver and the terminal devices must be raised to detect a fire and to give an alarm as soon as possible.
In a case of a plant consisting of a multiplicity of buildings or a large-scale building such as a skyscraper, a very large number of supervisory devices, such as fire detectors, and devices to be controlled are connected to the fire receiver through transmitters, or a multiplicity of analog detectors are connected to the fire receiver. If the building is enlarged or the layout is changed, the numbers of the supervisory terminals, the devices to be controlled, the transmitters and the analog fire detectors are increased or the contents to be displayed on the fire receiver are changed.
In the conventional arrangement in which a ROM in the fire receiver previously stores various information items (the addresses of the terminals, data about the contents to be displayed and data about linkage-control and the like) about the terminal devices, the enlargement of the building or the layout change of the building or the occupancy change of the same necessitates the ROM to be changed to another ROM on which novel data is written. At this time, a complicated operation of correctly writing various data items must be performed.
Therefore, it has been considered feasible to employ a fire alarm system in which: a representative transmitter is provided for each building or plural stories and a ROM is provided for each of the representative transmitters, or a ROM is provided for each transmitter, and various data about the portion covered by the transmitter is stored in the ROM of the transmitter, the fire receiver collects the various data stored in the ROM of each transmitter, and fire supervisory and control are performed in accordance with the collected data. As a result of the foregoing structure, the enlargement of the building necessitates only writing of various data about the subject portion on the ROM of a transmitter which is newly disposed. If the layout or the occupancy is changed, only various data in the ROM of the transmitter covering the subject portion must be changed. Therefore, an advantage can be realized in that the contents of the ROM of the transmitters except for the changed portions do not need to be changed.
However, a fire alarm system of the foregoing type must transmit information data stored in the ROM of each transmitter in addition to the-necessity of transmitting the fire information and the control information. If the foregoing various information items are transmitted with a fixed-length-signal as performed in the conventional system, the fact that the information data to be stored in the ROM is longer than the fire information and the control information raises a necessity of performing the data transmission operation while dividing the operation into plural times. Therefore, a problem arises in that a long time takes to complete the transmission. In particular, if information data is collected from all transmitters to periodically check whether or not information data collected by the fire receiver has an error, a problem arises in that it takes an excessively long time to transmit the data and in the meantime, the fire supervisory function cannot be performed.